Jesu, Joy of Man's Desiring [Jesu Bleibet Meine Freude], BWV.147 (Cramer)
Baroque. For bassoon but also playable on trombone or euphonium. Take a deep breath. This arrangement has the soloist performing the continuous melodic triplet figures throughout from the first measure to the second to last with no breaks other than a pair of 2½ bar rests on the first page otherwise it's batten down the hatches and compress that diaphragm cause you're almost there and... Phew. Bass clef with some tenor.